The invention relates to a collector segment at an end of which there is provided a contact surface to which a loop of a wire winding of an electric machine rotor is to be welded, preferably, by ultrasound welding. DE-OS 2,739,730 discloses a method of manufacturing of an armature of a dynamoelectrical machine according to which, contact elements of the armature winding are electrically and mechanically connected with collector segments by ultrasound welding. According to the method disclosed in DE-OS 2,739,730, conductors are secured by ultrasound welding either to the connecting ends of brush bearing surfaces or to, provided for this purpose, extension of the contact surface in segment recesses. Another method of providing as electrical contact so a mechanical connection of an armature winding with a collector segment is disclosed in DE-OS 3,017,426. DE-OS 3,017,426 also discloses using the ultrasound welding. According to the method disclosed in DE-OS 3,017,426, the collector segments are rolled on a contact surface of a sonotrode. Upon connection with segment hooks, the hooks that support wire winding loops, upon being rolled on by the sonotrode, are bent in the direction of the segment extension and are welded to the segments. The segment hooks should be made from a well-deformable material. To weld the hooks with segments, a considerable amount of heat is required. The heat can cause a thermal breakdown of the insulating material of the collector collar.